fs/dcache.c: adaptive vfs_cache_pressure on suspend / resume

[dorimanx-temasek]

adaptive vfs_cache_pressure on suspend / resume uses new power_suspend interface.

Low vfs_cache pressure values save battery while idle, while a low value also causes
stutter with longer up times.

Signed-off-by: UpInTheAir <upintheair.xda@gmail.com>

used commit: https://github.com/exynos7420/android_kernel_samsung_exynos7420/commit/d32d5b26ce013841da8a8aee41d47edff3562bad